1. Technical Field
The present invention relates to a head-mounted display device and a control method for the head-mounted display device.
2. Related Art
There is known a technique called augmented reality (AR) for adding information to a real environment and presenting the information using a computer. The augmented reality is installed in a smartphone, a head mounted display (hereinafter referred to as “head-mounted display device”), and the like. FIGS. 1A and 1B are explanatory diagrams for explaining the augmented reality. FIG. 1A shows a state in which the augmented reality is realized by a non-transmissive head-mounted display device. The head-mounted display device picks up an image of an outside scene using a camera, recognizes an image CP obtained by the image pickup, and generates information to be added and presented (in an example shown in the figure, objects OB). The head-mounted display device causes a liquid crystal screen to display an image obtained by superimposing the picked-up image CP and the generated objects OB. Consequently, a user of the head-mounted display device can experience the augmented reality. In the example explained herein, the augmented reality is realized using the non-transmissive head-mounted display device. However, the augmented reality can be realized by the smartphone and the like. For example, JP-A-2011-203823 discloses a non-transmissive head-mounted display device implemented with the technique of the augmented reality.
As another document disclosing the related art, there is JP-2010-146481.
FIG. 1B shows a state in which the augmented reality is realized by an optically transmissive head-mounted display device. Like the non-transmissive head-mounted display device, the optically transmissive head-mounted display device recognizes the image CP obtained by image pickup and generates information to be added and presented (the objects OB). Thereafter, the optically transmissive head-mounted display device causes a liquid crystal screen to display only the generated objects OB. A user visually recognizes both of the objects OB displayed on the liquid crystal screen and displayed as a virtual image VI and an outside scene SC seen through a lens in front of the user. Consequently, the user can experience the augmented reality. A region obtained by the image pickup shown in a first drawing from the left in FIG. 1B is referred to as “image pickup visual field” as well. A region displayed as the virtual image VI shown in a second drawing from the left in FIG. 1B is referred to as “video visual field” as well. A region recognizable as the outside scene SC shown in a third diagram from the left in FIG. 1B is referred to as “real visual field” as well.
In some cases, the size of a region where the virtual image VI is projected before the eyes of the user (a portion where the real visual field and the video visual field overlap) and the size of a region where image pickup can be performed by a camera (the image pickup visual field) do not coincide with each other. When the sizes of the regions do not coincide with each other, in the optically transmissive head-mounted display device, a shift occurs between the objects OB displayed as the virtual image VI and the outside scene SC seen through the lens before the eyes and gives a sense of discomfort to the user. Specifically, for example, when the region where image pickup can be performed by the camera (the video visual field) is broad, in the optically transmissive head-mounted display device in the past, the objects OB corresponding to the broad range are generated and displayed before the eyes of the user as the virtual image VI. In such a case, the user feels a sense or discomfort because of inconsistency that occurs between the outside scene SC in the region where the virtual image VI is projected before the eyes of the user (the portion where the real visual field and the video visual field overlap) and the objects OB.